Electrical discharge machining (EDM) is a particular type of CNC machine tool process. An EDM process shapes a workpiece by striking the workpiece with sparks emitted from an EDM electrode. The manner in which the sparks act upon the workpiece is determined by factors including the shape and position of the electrode. A complex workpiece feature, such as a turbine airfoil, may require a correspondingly complex shape for the electrode. If the electrode becomes worn through multiple EDM cycles, it can be restored to its original shape in a process known as redressing.